The present invention relates to a field emission micro-tip which can emit electrons uniformly and can be fabricated at a high yield when applied to a large device.
As an image display device to replace the cathode ray tube of existing television receivers, flat panel displays have been under vigorous development for use as in wall-mounted (tapestry) televisions and high definition televisions (HDTV).
Such flat panel displays include plasma display panels, liquid crystal displays, and field emission displays. Among these, the field emission display is widely used owing to the quality of its screen brightness and low power consumption.
Referring to FIG. 1, the structure of a conventional vertical field emission micro-tip will now be described.
The vertical field emission micro-tip includes a glass substrate 1, a cathode 2 formed on the glass substrate 1, a micro-tip 4 for field emission formed on cathode 2, an insulating layer 3 formed glass substrate 1 having a hole 3' surrounding micro-tip 4 on cathode 2, and a gate layer 5 formed on insulating layer 3 having an aperture 5' to allow field emission from micro-tip 4.
FIG. 2A is a vertical cross-section of a conventional horizontal field emission micro-tip and FIG. 2B is a plan view of the horizontal field emission micro-tip shown in FIG. 2A. As shown, in contrast with the vertical field emission micro-tip shown in FIG. 1, the structure of the horizontal field emission micro-tip has a cathode 10 and an anode 8 which are horizontally formed above a substrate 6 so that electrons are emitted horizontally with respect to the substrate 6.
The structure of the horizontal field emission micro-tip will now be described in detail.
An insulating layer 7 is formed on a glass substrate 6. A cathode 10 and an anode 8 are deposited on insulating layer 7 with a predetermined spacing. A hole 7' is formed on the insulating layer 7 between cathode 10 and anode 8 to a predetermined depth. A gate electrode 9 is provided within hole 7' to control electron emission from cathode 10 to anode 8.
In the case of vertical field emission micro-tip using a single tip as shown in FIG. 1, since the flow of electron beams depends on the size of gate aperture 5' a fabrication technique applicable to a micro-tip with several tens of nanometers in diameter is desired. In other words, in order to fabricate a high-precision gate aperture for the vertical field emission micro-tip of several tens of nanometers, a highly advanced microfabrication technique of submicron units is necessary. Thus, there are problems such as non-uniformity throughout the fabrication process and a lowered yield when fabricating larger devices. Also, if the gate aperture is larger, a higher level of bias voltage must be applied to the gate, thereby necessitating a higher voltage for driving the device.
The horizontal field emission micro-tip shown in FIG. 2A has a higher yield and a more uniform structure, compared with the vertical field emission micro-tip. However, variable application of the horizontal field emission micro-tip is difficult, since the flow of electrons is restricted to a single horizontal direction. As a result electron beam application using the horizontal field emission micro-tip is very difficult.